input type radio checked

i have this:

<xsl:for-each select="registro">
<input type="radio" name="votacionvalor" value="{valorrespuesta}"/>
<xsl:value-of select="respuesta"/><br />
</xsl:for-each>

in this method i load 25 input radio type.
how can i always the fist radio put in checked mode?
(<input type="radio" name="votacionvalor" value="{valorrespuesta}"
checked="checked"  />)
only in the fist radio.
is posible?
how?
thanks



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